xref: /openbmc/linux/arch/arm/kernel/head-common.S (revision a1e58bbd) 
1/*
2 *  linux/arch/arm/kernel/head-common.S
3 *
4 *  Copyright (C) 1994-2002 Russell King
5 *  Copyright (c) 2003 ARM Limited
6 *  All Rights Reserved
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 *
12 */
13
14#define ATAG_CORE 0x54410001
15#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
16
17	.type	__switch_data, %object
18__switch_data:
19	.long	__mmap_switched
20	.long	__data_loc			@ r4
21	.long	__data_start			@ r5
22	.long	__bss_start			@ r6
23	.long	_end				@ r7
24	.long	processor_id			@ r4
25	.long	__machine_arch_type		@ r5
26	.long	__atags_pointer			@ r6
27	.long	cr_alignment			@ r7
28	.long	init_thread_union + THREAD_START_SP @ sp
29
30/*
31 * The following fragment of code is executed with the MMU on in MMU mode,
32 * and uses absolute addresses; this is not position independent.
33 *
34 *  r0  = cp#15 control register
35 *  r1  = machine ID
36 *  r2  = atags pointer
37 *  r9  = processor ID
38 */
39	.type	__mmap_switched, %function
40__mmap_switched:
41	adr	r3, __switch_data + 4
42
43	ldmia	r3!, {r4, r5, r6, r7}
44	cmp	r4, r5				@ Copy data segment if needed
451:	cmpne	r5, r6
46	ldrne	fp, [r4], #4
47	strne	fp, [r5], #4
48	bne	1b
49
50	mov	fp, #0				@ Clear BSS (and zero fp)
511:	cmp	r6, r7
52	strcc	fp, [r6],#4
53	bcc	1b
54
55	ldmia	r3, {r4, r5, r6, r7, sp}
56	str	r9, [r4]			@ Save processor ID
57	str	r1, [r5]			@ Save machine type
58	str	r2, [r6]			@ Save atags pointer
59	bic	r4, r0, #CR_A			@ Clear 'A' bit
60	stmia	r7, {r0, r4}			@ Save control register values
61	b	start_kernel
62
63/*
64 * Exception handling.  Something went wrong and we can't proceed.  We
65 * ought to tell the user, but since we don't have any guarantee that
66 * we're even running on the right architecture, we do virtually nothing.
67 *
68 * If CONFIG_DEBUG_LL is set we try to print out something about the error
69 * and hope for the best (useful if bootloader fails to pass a proper
70 * machine ID for example).
71 */
72
73	.type	__error_p, %function
74__error_p:
75#ifdef CONFIG_DEBUG_LL
76	adr	r0, str_p1
77	bl	printascii
78	b	__error
79str_p1:	.asciz	"\nError: unrecognized/unsupported processor variant.\n"
80	.align
81#endif
82
83	.type	__error_a, %function
84__error_a:
85#ifdef CONFIG_DEBUG_LL
86	mov	r4, r1				@ preserve machine ID
87	adr	r0, str_a1
88	bl	printascii
89	mov	r0, r4
90	bl	printhex8
91	adr	r0, str_a2
92	bl	printascii
93	adr	r3, 3f
94	ldmia	r3, {r4, r5, r6}		@ get machine desc list
95	sub	r4, r3, r4			@ get offset between virt&phys
96	add	r5, r5, r4			@ convert virt addresses to
97	add	r6, r6, r4			@ physical address space
981:	ldr	r0, [r5, #MACHINFO_TYPE]	@ get machine type
99	bl	printhex8
100	mov	r0, #'\t'
101	bl	printch
102	ldr     r0, [r5, #MACHINFO_NAME]	@ get machine name
103	add	r0, r0, r4
104	bl	printascii
105	mov	r0, #'\n'
106	bl	printch
107	add	r5, r5, #SIZEOF_MACHINE_DESC	@ next machine_desc
108	cmp	r5, r6
109	blo	1b
110	adr	r0, str_a3
111	bl	printascii
112	b	__error
113str_a1:	.asciz	"\nError: unrecognized/unsupported machine ID (r1 = 0x"
114str_a2:	.asciz	").\n\nAvailable machine support:\n\nID (hex)\tNAME\n"
115str_a3:	.asciz	"\nPlease check your kernel config and/or bootloader.\n"
116	.align
117#endif
118
119	.type	__error, %function
120__error:
121#ifdef CONFIG_ARCH_RPC
122/*
123 * Turn the screen red on a error - RiscPC only.
124 */
125	mov	r0, #0x02000000
126	mov	r3, #0x11
127	orr	r3, r3, r3, lsl #8
128	orr	r3, r3, r3, lsl #16
129	str	r3, [r0], #4
130	str	r3, [r0], #4
131	str	r3, [r0], #4
132	str	r3, [r0], #4
133#endif
1341:	mov	r0, r0
135	b	1b
136
137
138/*
139 * Read processor ID register (CP#15, CR0), and look up in the linker-built
140 * supported processor list.  Note that we can't use the absolute addresses
141 * for the __proc_info lists since we aren't running with the MMU on
142 * (and therefore, we are not in the correct address space).  We have to
143 * calculate the offset.
144 *
145 *	r9 = cpuid
146 * Returns:
147 *	r3, r4, r6 corrupted
148 *	r5 = proc_info pointer in physical address space
149 *	r9 = cpuid (preserved)
150 */
151	.type	__lookup_processor_type, %function
152__lookup_processor_type:
153	adr	r3, 3f
154	ldmda	r3, {r5 - r7}
155	sub	r3, r3, r7			@ get offset between virt&phys
156	add	r5, r5, r3			@ convert virt addresses to
157	add	r6, r6, r3			@ physical address space
1581:	ldmia	r5, {r3, r4}			@ value, mask
159	and	r4, r4, r9			@ mask wanted bits
160	teq	r3, r4
161	beq	2f
162	add	r5, r5, #PROC_INFO_SZ		@ sizeof(proc_info_list)
163	cmp	r5, r6
164	blo	1b
165	mov	r5, #0				@ unknown processor
1662:	mov	pc, lr
167
168/*
169 * This provides a C-API version of the above function.
170 */
171ENTRY(lookup_processor_type)
172	stmfd	sp!, {r4 - r7, r9, lr}
173	mov	r9, r0
174	bl	__lookup_processor_type
175	mov	r0, r5
176	ldmfd	sp!, {r4 - r7, r9, pc}
177
178/*
179 * Look in include/asm-arm/procinfo.h and arch/arm/kernel/arch.[ch] for
180 * more information about the __proc_info and __arch_info structures.
181 */
182	.long	__proc_info_begin
183	.long	__proc_info_end
1843:	.long	.
185	.long	__arch_info_begin
186	.long	__arch_info_end
187
188/*
189 * Lookup machine architecture in the linker-build list of architectures.
190 * Note that we can't use the absolute addresses for the __arch_info
191 * lists since we aren't running with the MMU on (and therefore, we are
192 * not in the correct address space).  We have to calculate the offset.
193 *
194 *  r1 = machine architecture number
195 * Returns:
196 *  r3, r4, r6 corrupted
197 *  r5 = mach_info pointer in physical address space
198 */
199	.type	__lookup_machine_type, %function
200__lookup_machine_type:
201	adr	r3, 3b
202	ldmia	r3, {r4, r5, r6}
203	sub	r3, r3, r4			@ get offset between virt&phys
204	add	r5, r5, r3			@ convert virt addresses to
205	add	r6, r6, r3			@ physical address space
2061:	ldr	r3, [r5, #MACHINFO_TYPE]	@ get machine type
207	teq	r3, r1				@ matches loader number?
208	beq	2f				@ found
209	add	r5, r5, #SIZEOF_MACHINE_DESC	@ next machine_desc
210	cmp	r5, r6
211	blo	1b
212	mov	r5, #0				@ unknown machine
2132:	mov	pc, lr
214
215/*
216 * This provides a C-API version of the above function.
217 */
218ENTRY(lookup_machine_type)
219	stmfd	sp!, {r4 - r6, lr}
220	mov	r1, r0
221	bl	__lookup_machine_type
222	mov	r0, r5
223	ldmfd	sp!, {r4 - r6, pc}
224
225/* Determine validity of the r2 atags pointer.  The heuristic requires
226 * that the pointer be aligned, in the first 16k of physical RAM and
227 * that the ATAG_CORE marker is first and present.  Future revisions
228 * of this function may be more lenient with the physical address and
229 * may also be able to move the ATAGS block if necessary.
230 *
231 * r8  = machinfo
232 *
233 * Returns:
234 *  r2 either valid atags pointer, or zero
235 *  r5, r6 corrupted
236 */
237
238	.type	__vet_atags, %function
239__vet_atags:
240	tst	r2, #0x3			@ aligned?
241	bne	1f
242
243	ldr	r5, [r2, #0]			@ is first tag ATAG_CORE?
244	subs	r5, r5, #ATAG_CORE_SIZE
245	bne	1f
246	ldr	r5, [r2, #4]
247	ldr	r6, =ATAG_CORE
248	cmp	r5, r6
249	bne	1f
250
251	mov	pc, lr				@ atag pointer is ok
252
2531:	mov	r2, #0
254	mov	pc, lr
255